DESCRIPTION: Surgical procedures to modify corneal curvature for the correction of myopia, hyperopia and astigmatism are hampered by limited accuracy of results. Substantial variability of effect is seen with surgical procedures such as radial keratotomy, in which corneal deformation occurs in response to corneal incisions. If the procedures were based on measures of the biomechanical properties of the cornea, results would be improved, since such measures can be used to predict preoperatively the magnitude of the response of the cornea to surgery. The goal of this research is to precisely define the relationship of the mechanical properties of individual corneas to their response to surgery. The ultrasonic energy technique will be used to measure wave velocity within the cornea, allowing precise non-destructive measurement of corneal mechanical properties in vivo. The effects on these properties of biological variables, such as age and pathological corneal states (e.g. keratoconus) will be determined. Measured mechanical properties will be used in a computer finite element model to predict responses of individual corneas to surgery. The research team consists of an engineer with expertise in ultrasound instrumentation, a mechanical engineer with expertise in mathematical modeling and an ophthalmologist with expertise in corneal surgery and research.